[Influence of removal of Na from the bath solution on the antispasmodic actions of isoproterenol and papaverine, with special reference to their relations to Ca (experiments using the isolated rat rectum)].

Influence of the Na removal from bath solution on the antispasmodic actions of isoproterenol and papaverine against the phasic contractions by K and acetylcholine were investigated in relation to the mobilization of Ca in isolated rectal strip from the rat. Effect of the Na removal on the uptake of intracellular Ca into storage sites was also examined. The Na removal attenuated the inhibitory actions of isoproterenol and papaverine on the release of Ca, whereas the Na removal did not affect the inhibitory action of isoproterenol on Ca influx and that of papaverine on the response of the muscle contractile elements. Furthermore, the Na removal inhibited the uptake of intracellular Ca into storage sites. Thus, it is suggested that isoproterenol and papaverine may generate the inhibitory action on the release of Ca by accelerating Ca uptake into storage sites, therefore the antispasmodic actions of these agents are depressed by the deprivation of Na from the bath solution which attenuates the Ca uptake.